Ionic discharge tube



Feb. 23, 1937. J. E HENDERSON ET AL 2,0711464 IONIC DISCHARGE TUBE FiledMay 29. 1933 2 Sheets-Sheet 1 INVENTORS .lEHendersum ATTORNEYS.

Feb. 23, 19.37. .1. E. HENDERSON ET AL 2,071,464

IONIC DISCHARGE TUBE Fil'ed May 29, 1931 2 Sheets-Sheet 2 l6 INVENTORS2a I.E.HET1 dEISElTL ATTRNEYs.

Patented Feb. 23, 1937 UNITED STATES PATENT OFFICE Seattle, Wash.,

assignors to Barkon Tube Lighting Corporation, Seattle, Wash., 'acorporation Application May 29, 1931, Serial No. 541,040

3 Claims.

The present invention relates to luminous tubes of the type generallyreferred to as spectral discharg or ionic discharge tubes. By ourinvention, we provide a luminous ionic discharge tube and a system ofoperation therefor in which electrical energy is supplied to theluminous gases by means of a large area conductor separated from the gasby a wall of dielectric material. By the use of such anelectrode, anygas which is stable under the action of an electrical discharge may beused as the illuminant, including the socalled active gases, becausethere is no contact between the gases and the conductor. Preferably thegas which we use may be entirely or in part carbon dioxide, since such agas, when ionized, gives a light approximating daylight, but it is to beunderstood that any other stable gas may be used.

We. have found that, in order to pass through the gas in the tubesufficient 'current to give a steady and brilliant light, the electrodearea must be very large as compared with the cross-sectional area of theluminous tube if a source of supply with the ordinary commercialfrequencies is to be used. I

Electrostatic capacity electrodes for ionic discharge tubes as they havebeen suggested in the prior art, have been termed conducting caps withthe caps covering as much as 40% of the tube length in extreme cases.Using the same ter-- minology to refer to the tube lighting systemherein disclosed, the conducting caps would have to cover approximatelyof the length of the tube in order to obtain a steady and brilliantlight, such as is desirable, and obviously such a length of tube devotedto the electrode would be undesirable.

It is one of the features of our invention to provide such an electrodeas will have sufficient area to give the desired illumination and,,atthe. same time, have it compact enough so as not to occupy an undueamount of space.

We have also found that in such a tube with such large electrodes, theuse of the ordinarytransformer by which the voltage of a current supplyof commercial frequencies is stepped up to the necessary potential ishighly undesirable,if

not impossible, because of. the resulting unsteadithat this may beovercome by associating inductance with the external circuit, preferablyin an amount sufficient to cause the current through the tube and theelectromotive force to be substantially in phase. In this way, theeffect of the 5 large electrostatic capacity, due to the large areaelectrodes, is substantially neutralized.

While the necessary inductance may be provided independently of thetransformer, we have found it convenient to utilize the transformer 10itself for this purpose. In order to accomplish this, we have found thata transformer having the proper amount of magnetic leakage can be used.

We have also found that good results may be 15 obtained when the currentin the tube and the electromotive force are not exactly in phase, but,in such case, it is desirable to protect the windings of the transformeragainst puncturing which we have found to occur, under suchcircumstances, in the outside windings of the secondary of thetransformer. To prevent such puncturing, we preferably provide atransformer in which these outside windings are more heavily insulatedthan the remainder of the windings. 25

Preferably we obtain the large surface area electrode by means of aplurality of small diameter tubes, each connected to the luminous tube,so that the interior of each small tube will be in communication withthe interior of the luminous 30 tube. By using small diameter tubes forthe electrode portion, we are able to make the walls thereof thinnerthan the walls of the luminous tube, with a corresponding increase inthe electrostatic capacity. Furthermore, by associating thesev smalltubes in parallel groups, as we prefer to do, we are able to supporteach tube by the adjacent tubes by providing a material to bridge overthe spaces therebetween. The net result of our preferred arrangement isa compact group of small tubes, each of which, while thin and fragileand connected at one end only to the luminous tube, may nevertheless besupported in such a manner that a considerable strength to resistbreakage is provided. 45

Our invention will be best understood from the following description ofillustrative embodi- 'ments of our invention.

In the drawings:--

Figure 1 is a diagrammatic view showing the preferred form of luminousor ionic discharge tube and associated electrical circuit arrangement.

Figure 2 is an enlarged view, partly in side elevation and partly ,inlongitudinal section, of one of the electrodes.

Figure 3 is an enlarged fragmentary transverse section on the line 3-3of Figure 2.

Figure 4 is an enlarged fragmentary section on the line 44 of Figure 2.

Figure 5 is a view part in section and part in elevation of theelectrode and showing a further method of operating the electrodes.

Figure 6 is a viewpf a type of the transformer that may be employed.

Figure 7 is a section on the line 1-1 of Figure 6.

Figure 8 is a purely diagrammatic view illustrating the method ofWinding for the secondary coils of the transformer.

Figure 9 shows a modified form of electrode.

Figures 10 and 11 are enlarged fragmentary views on the respective linesin Figure 9 showing detailed features of construction.

Referring to the drawings in detail, and wherein similar referencecharacters designate corresponding parts thruout the several views, andreferring particularly to the form of invention disclosed in Figures 1to 8 inclusive, the letter A designates the luminous tube provided atits ends with the electrodes B. The tube A is preferably formed of glassand may be of any desired form and size desired in accordance with thetype of illumination desired for the luminous portion of the tube. Theelectrodes B are shown connected in circuit with a transformer C ofspecial construction which is for connection with a supply of lowfrequency low voltage alternating current, say of sixty cycle such asordinarily supplied for commercial use.

Referring now to the specific construction of the large area capacityelectrode B, which we have chosen for purposes of illustration, the sameis made of a dielectric material such as glass and in one'practical sizehas an approximate dimension of eighteen inches in length and threeinches in diameter. The electrode comprises a bell cap 5 for connectionto an end of the tube A. The lower side of the hollow bell cap 5 isclosed by a flat disc 6 to the under side of which is sealed a largenumber of small tubes I havin walls much thinner than the walls of thetube A. These small tubes 1 are closed at their lower ends and havetheir upper ends in communication with the interior of the hollow bellcap 5 thru apertures 8 formed thru the disc 6. These thin walled tubes 1are of equal length and formed of a suitable di-electric material suchas glass. By way of example, there may be about one hundred and fifty ofthese thin walled tubes 1 of about 3 mm. diameter connected in slightlyspaced-apart relation to each other. This compact "bundling of the smalltubes 1 provides a very large area electrode as to external surface areacompared with the volume of the electrode as a whole.

While various forms of the so-called active gases may be employed, weprefer to use carbon dioxide, but it is to be distinctly understood thatany gases which are stable under the action of electrical discharge maybe employed. As will be observed, the interior of the electrode tubes 1are in communication with the interior of the tube A and thatthe'electrode tubes form terminals of the container for the'gas to beionized.

In the specific form illustrated, the plurality of small electrode tubes1 are sealed within a capsule-like container or casing [0, preferablyformed of a non-conducting material, such as glass, and, in the exampleshown, it is of tubular formation and is closed at its lower end. Thiscasing I0 is sealed at its upper end to the hollow bell cap 5 and has aninternal diameter slightly greater than the diameter of the group ofelectrode tubes 1 whereby the outermost annular series of the tubes arespaced slightly from the inner wall of the casing ID. The upperextremity of the casing is provided with an outwardlypressed annularbead ll providing an annular internal pocket about the upper extremityof the tubes 1. The lower end of the casing extends "slightly below theclosed ends of the tubes 1 to provide a small chamber for a purpose tobe subsequently explained.

The container or casing ill may be completely filled with a plastic massof conducting material [2 forming a conductor for transfer of electricalenergy to the gas to be ionized. By way of example, the mass may be agarmixed with salt water, this material being sufficiently stiff under thetemperatures developed in the electrode to provide desired support forthe tubes 1. In the form shown in Fig. 3 this plastic conductor l2completely fills the casing l0 and entirely encircles each of the smallelectrode tubes 1. In the form shown in Figure 5, the casing I0 is onlypartially filled with the pastic conducting material l2 so as to form asupport for the lower ends of the small electrode tubes 1, the remainingmajor portion of the casing being filled with either a luminous ornon-luminous gaseous conductor such as neon or a liquid conductor suchas water, if so desired. The pressure of the gaseous conductor used inthe casing is not material. While it is preferred that the casing shallcontain a sufficient quantity of the plastic conducting material to forma support for the electrode tubes 1, such material may be omitted andthe casin may be filled completely with a gaseous or a liquid conductor.

For the purpose of filling the casing in with either a solid, liquid orgaseous conductor, it is provided at its upper end upon the bead II witha tip 13 and at its lower end with a tip M. In the manufacture of theelectrode, the tips I3 and I4 are open, permitting the conductingmaterial to be inserted through the tip l3 and the air in the casing tobe expelled through the tip I4. After the casing is completely filledwith the conducting material, the tip i4 is sealed off and the tip l3may be also sealed off, as by heating. The tip l4 serves as an entranceopening for a lead-in wire having its end terminating in a coil or aplate of suitable area in the chamber formed below the tubes 1. Thisterminal conductor or plate I5 is in electrical contact with theconducting material l2. The tip 14 may be sealed about the lead-in wire.

The large number of small electrode tubes 1 form in effect a partitionof large area between the conducting material l2 and the gas containedin the tube. This constitutes a condenser of considerable capacity, theconducting material l2 and the gas inside the tubes 1 being the platesand the walls of the tubes 1 being the dielectric.

As illustrated in Fig. 1, current is preferably supplied to our luminoustube by means of a transformer, one form of which is illustrated at C.

The primary 2| of the transformer is supplied preferably from acommercial source of alternating current 23, which may be a sixty cyclealternating current, such as is generally supplied for commercial use.The secondary coils I9 are wound on the core leg I! of the core l8, oneon each side of the primary winding, the wires 20 bil extending from therespective secondaries to the respective electrodes B.

As we have already said, we have found that, if the transformer C is ofthe usual type, the light resulting from such an arrangement isunsteady, and that we have found that this difliculty can be overcome byassociating inductance with the circuit.

In the arrangement illustrated, this inductance is provided by variablemagnetic shunts produced by a series of soft iron plates 24 between theprimary and the secondary windings, these plates being designed to giveto the transformer the desired inductance to neutralize, or partiallyneutralize, the electrical effect of the large capacity electrodes.

In order to minimize the possibility of a potential breakdown in thecircuit, we preferably insulate the outer turns of each secondarywinding to a, greater extent than the remainder of the windings of thesecondary, as diagrammatically illustrated in Fig. 8. This greaterinsulation may be provided by spacing the outer windings a greaterdistance apart than the inner windings of the coil,- by providing aheavier coating of insulation on the wire of these outer windings and bysheets of insulating material, as at l9, or by any one or more of thesemethods.

Referring now to the form of capacity or condenser electrode shown inFigures 9, 10 and 11 the casing shown in Figures 2 and is dispensed withand the grouped series of small electrode tubes 1' are connected to andare in communication with a hollow bell cap 5 for connection with theends of the light tube A as in Figure l. The tubes 1' are coated with ametallic material 30, such as aluminum paint, carbon or graphitecompositions, to provide a conducting coating upon the entire externalsurface of the tubes. After the metallic coating is applied, the tubesmay be coated with one or more layers of lacquer or other suitablematerial to provide an insulating coating about and between the tubes toinsulate the tubes against brush discharge and resultant production ofozone and consequent waste of energy. This coating of insulation alsoforms a binder for the tubes as shown in Figure 11 and reduces to aminimum the possibility of a tube being broken. Prior to application ofthe insulating coating 3-2, a terminal conductor 35 is electricallyconnected with the metallic coatings 30 at a point preferably midway theends of the tubes 3'. This terminal 35 may consist cf strands of wiresuitably interwoven between the tubes i so as to contact with themetallic coating of each tube as shown in Figure 10. This interweavingof the Wire 35 serves as a further reinforcement for the relativelysmall electrode tubes 71'.

it will be noted that the electrode shown in Figures 9, l0 and 11 doesnot difi'er to any great extent from the form shown in Figure 2 asidefrom the omission of the casing i0 permitting use of liquids, plasticand gaseous forms of conductors in connection with the bundledarrangement of small electrode tubes. In each form of electrode, thebasic idea is retained; i. e., the provision of an electrode having avery large external surface area when compared with the overalldimensions of the electrode.

By our invention, the capacity of the condenser electrodes is notonlyincreased much beyond the prior art practices, but the electrodesare'also changed as to form and adaptability to various commercial uses.

When the electrode capacity is equivalent to that given by to feet of 25mm. thin-walled glass tubing, electrical surges and flickering in thetube begin to be of importance and, as electrode capacities increase, itbecomes essential to change the inductance of the circuit to an extentnot heretofore known in the prior art of luminous tubes. When, however,sufilcient inductance is provided, a luminous tube of satisfactorybrilliance and steadiness is attained. For example, in tests with one ofour lamps, with forty feet of light tube, 10 mm. in diameter, with animpressed voltage of 15,000 volts, and with the adjustment of inductanceproperly made, and each electrode having one hundred feet of 25 mm.tubing, approximately 350 milliamperes of cur-- rent flows. 'Under theseconditions, the intensity of illumination emitted by one foot of thelight tube, at a distance of one foot, is sixteen foot being 5 mm. indiameter and about 27 inches long, each electrode having an area ofapproximately 18,000 sq. cm. From this example,v the large ratio betweenthe area of our large capacity electrodes as compared with its volumewill be evident.

It will be understood that, since nothing is in contact with the gas tobe ionized except the glass walls, our tubes have an indefinitely longlife.

Changes in the shape, size and arrangement of parts may be made to theform of invention herein shown and described, without departing from thespirit of the invention or the scope of the following claims.

We claim:

1. A luminous ionic discharge tube having a compact dielectric electrodefor illuminating the gas in the tube, said electrode comprising aplurality of closely spaced small electrode tubes of dielectricmaterial, each electrode tube being closed at one end and having itsother end connected to the luminous tube, and a conducting materialsurrounding and contacting with the whole exterior of each of saidelectrode tubes, the material around any one tube being of a solidnature and being in contact with the material around adjacent tubes,whereby each tube is supported by adjacent tubes.

2. A. luminous ionic discharge tube having a dielectric electrode forilluminating the gas in the tube, said electrode comprising a pluralityof electrode tubes of dielectric material, each electrode tube beingclosed at one end and having its other end connected to the luminoustube, the electrode tubes being arranged in a group side by side, acontainer surrounding the group, a plastic conducting material in thecontainer and covering at least the sealed ends of the tubes in thegroup to support the same, substantially the remainder of the containeralso being filled with conducting material.

3. A luminous ionic discha ge tube having a dielectric electrode forilluminating the gas in the tube, said electrode comprising a pluralityof electrode tubes of dielectric material with the interior of each ofthe electrode tubes in communication with the interior of the luminoustube, conducting material contacting with the exterior of each electrodetube and a casing in which said electrode tubes and conducting materialare located, said conducting material being in contact with the insidesurface of said casing and being supported thereby.

JOSEPH E. HENDERSON. BROUSSAIS C. BECK.

